Bioprocess and Biosystems Engineering最新文献

There is significant interest in employing cyanobacteria for eco-friendly biofuel production, utilizing CO₂ and sunlight. Recent advancements highlight the advantages of pathway engineering in cyanobacteria in enhancing the yields of biobutanol from the engineered strains. Isobutanol has excellent potential as an alternative fuel and can be blended with gasoline in ratios reaching 100% for use in existing internal combustion engines (ICE). This research focuses on the genetic engineering of Synechocystis sp. PCC 6803 to create mutant strains impaired in PHB synthesis but can biosynthesize isobutanol through an incorporated 2-keto-acid pathway in their genome. The synthesis of isobutanol is achieved through the heterologous expression of α-ketoisovalerate decarboxylase (Kivd) and alcohol dehydrogenase (Yqhd), both driven by the strong, light-inducible psbA2 promoter. The PHB synthase mutant strain ECDM12, which produces isobutanol, showed a 3.8-fold higher titer than PHB-synthesizing strains under identical cultivation conditions. Indoor cultivation in a 2 L photobioreactor (PBR) under simulated diurnal light resulted in the highest titer of 687.6 mg L^-1 (11th day) and productivity of 64.1 mg L^-1 day^-1. Outdoor studies in PBR under natural sunlight resulted in a maximum titer of 398 mg L^-1 (15th day) and productivity of 33.7 mg L^-1 day^-1, marking the first photosynthetic isobutanol production under natural sunlight.

Membrane proteins (MPs) are essential for various cellular functions and therefore critical targets for the drug industry. However structural and functional studies of MPs are challenging due to the difficulty and cost of solubilization and purification. Effective solubilization typically requires the incorporation of MPs into detergent micelles. Despite that this is a common practice, it has the potential to destabilize MPs. Alternatively, detergent-free systems have emerged, and reconstitution of MPs in Amphipol (APol) is one of the common methods. Polystyrene beads are generally used for this purpose. We investigated and evaluated the effectiveness of polydivinylbenzene Purolite™ PuroSorb™ PAD600 beads for detergent removal in membrane protein solubilization. To accomplish this, the membrane protein FtsH, solubilized in either DDM or LMNG, was exchanged with varying concentrations of APol, and detergents were removed by Purolite™ PuroSorb™ PAD600 beads. The results demonstrate that Purolite™ PuroSorb™ PAD600 beads are effective for detergent removal when the mass ratio of the Membrane Protein:Amphipol (MP:APol) is increased up to 1:10. The usage of Purolite™ PuroSorb™ PAD600 beads supports biochemical applications for membrane protein isolation and purification studies.

Single-cell protein (SCP) produced by yeast using low-cost agricultural wastes shows great potential as an alternative protein source for animal and human nutrition. In this study, we developed an adaptive evolution method coupled with centrifugal fractionation and pH shifting to enhance SCP production by Trichosporon cutaneum from wheat straw. During the adaptive evolution, the culture pH was shifted from 5.0 to 7.0, which is more favorable for SCP accumulation of T. cutaneum. The finally obtained T. cutaneum CL160 exhibited a 109.2% increase in SCP content compared to the parental strain. The DCW and SCP titer of T. cutaneum CL160 reached 48.6 ± 1.5 g/L and 14.2 ± 1.1 g/L using wheat straw clarified hydrolysate by batch fermentation. Fed-batch fermentation using wheat straw-derived syrup further improved DCW and SCP titer to 124.2 g/L and 32.6 g/L. Further attempts were performed to prepare soluble yeast extract from lignocellulose-derived SCP by cell autolysis. This yeast extract served as an effective nitrogen source for lactic acid fermentation by Pediococcus acidilactici, achieving 83.2 ± 1.1 g/L lactic acid titer and 45 × 10⁹/mL CFU value, comparable to commercial yeast extract. This study demonstrates the conversion of waste lignocellulosic feedstocks into sustainable SCP and soluble yeast extract, presenting an innovative strategy for the valorization of non-food lignocellulosic feedstocks.

Simultaneous nitrification and denitrification (SND) processes represent a promising approach for nitrogen removal from effluents characterized by a low COD/N ratio, especially when combined with fixed-bed reactors to ensure that slow-growing biomass (e.g., nitrifiers) is not washed out. In this reactor configuration, biofilms are formed, which promote mass transport of the substrates involved in SND. Therefore, understanding the effective diffusivity of ammonia through the biofilm is essential to improve nitrogen removal, as it is influenced by the thickness of the support media and biomass growth, particularly under counter-diffusion conditions. For this type of study, flow cells (units for study particularities of a bioreactor) are used, as they provide greater operational control of the process. To evaluate this issue, were operated three flow cells for 234 days, each one with different thicknesses of polyurethane foam (i.e., 2 mm, 5 mm and 10 mm) as a support media for SND adhered biomass. Within each flow cell, the foam serves to segregate the aerated and non-aerated zones, thereby inducing counter-diffusion. Throughout operation, tests were conducted to estimate the effective diffusivity factor (EDF) of ammonia in the biofilm using the AQUASIM software. Routine analyses demonstrated that the average removal of organic matter and ammoniacal nitrogen were 73%, 68%, 57%, and 66%, 54%, 34% in the 2, 5, and 10 flow cells, respectively. Furthermore, EDF estimation tests demonstrated a 95% reduction in ammonia diffusivity over operating time, attributable to pore clogging induced by heterotrophic biomass growth within the support media. The decline in EDF of ammonia exerted a substantial impact on the total nitrogen removal and, consequently, on the performance of the simultaneous nitrification and denitrification process. Thus, the importance of considering mass transport phenomena in reactor designs with support media and long operating times, i.e., with biofilm growth and establishment, becomes evident.

The goal of the present study was to define better conditions for the invertase production from the yeast Rhodotorula toruloides in the surface adhesion fermentation (SAF) in the presence of magnetic chitosan-coated (MnFe₂O₄-Ch) manganese ferrite nanoparticles and to evaluate their reuse in different fermentation cycles. The synthesis of MnFe₂O₄-Ch was performed using the one-step chemical coprecipitation method, which was assisted with hydrothermal treatment. Box-Behnken design was applied to establish the relationship between the selected parameters. The reuse of the immobilized biomass was evaluated with and without the MnFe₂O₄-Ch addition in several fermentation cycles. According to X-ray diffraction results, the MnFe₂O₄-Ch exhibited a spinel structure with a crystallite size of 20.73 nm. The mean particle hydrodynamic size was 181.7 nm, the magnetic saturation was measured to be 39.6 emu/g at 20 kOe and 300 K. The growth of R. toruloides microorganism was stimulated with MnFe₂O₄-Ch, and a more significant effect was observed at the concentration of 2 mg/mL. The microorganism produced an invertase enzyme, and higher enzyme activity (1.88 IU/mL) was detected with the MnFe₂O₄-Ch at 1 mg/mL. The enzymatic activity increased by 69% in surface adhesion fermentation compared to submerged fermentation. In the third cycle of SAF with reused immobilized yeast and MnFe₂O₄-Ch addition, the enzymatic activity increased compared to the first two cycles of reuse, reaching values without significant difference compared to the enzymatic activity in the initial SAF. Surface adhesion fermentation may be an appropriate method to improve invertase production from R. toruloides.

Hepatocellular carcinoma (HepG2) is a highly aggressive liver cancer with poor prognosis, limited treatment options, and high mortality rates, making it a serious global health concern that demands urgent development of more effective and safer therapeutic approaches. In this context, the present study focuses on the green synthesis of SrO2 nanoparticles using Clitoria ternatea flower extract, followed by surface modification with Pluronic F127 (PF127) and L-histidine (LH), to fabricate SrO2-PF127-LH nanocomposites aimed at evaluating their potential anticancer efficacy against the HepG2 cell line. Various analytical techniques were used to characterize the nanocomposite, and then their anticancer activity against HePG2 liver cancer cells, antioxidant properties, and antimicrobial activity against the bacteria mentioned above were evaluated. XRD revealed the crystalline nature of SrO₂ with a tetragonal phase. FTIR spectrum confirmed the Sr-O stretching band at 573 cm^-1 for SrO₂-PF127-LH nanocomposite. UV-visible analysis revealed the band gap energies of 4.13 eV for SrO₂ and 4.07 eV for SrO₂-PF127-LH nanocomposite. The surface defects including oxygen vacancies of SrO₂-PF127-LH nanocomposite were investigated using PL analysis. The SrO₂-PF127-LH nanocomposite exhibited excellent antibacterial and antioxidant activities when compared to SrO₂ nanoparticles alone. In addition, the SrO₂-PF127-LH nanocomposite had enhanced anticancer activity against liver cancer (HePG2) cell lines.

Saccharomyces cerevisiae is indispensable to industrial fermentation; however, many existing models fail to adequately represent the metabolic complexity of its growth on mixed carbon sources in defined media. In this study, we introduce a novel hybrid modeling framework for the batch cultivation of S. cerevisiae, utilizing sucrose, glucose, and fructose as carbon sources, and urea as a nitrogen source. The model decisively captures critical phenomena under aerobic conditions, including the Crabtree effect, diauxic shifts, and sequential sugar utilization-critical areas frequently oversimplified in current models. By integrating mechanistic kinetics with data-driven enhancements, the hybrid model significantly improves predictive accuracy relative to the purely mechanistic baseline, reducing the average prediction error by a factor of 1.9 during training and 2.0 during testing. This framework enables detailed simulation of culture dynamics and was carefully designed for modular integration into digital twin platforms and automated control systems, aligning perfectly with Industry 4.0 biomanufacturing trends. Furthermore, the model's validation under conditions pertinent to emerging bioeconomies, such as those in Latin America, underscores its industrial applicability. Overall, this work delivers a scalable and precise tool for optimizing yeast-based bioprocesses, carrying significant implications for defined media formulation, metabolic engineering, and digital fermentation technologies.

The production of a functional ingredient (FI) containing Lactobacillus acidophilus (ATCC 4356) immobilised in oat bran was designed and optimised. The effects of the independent variables, incubation time and hydration level, were analysed and optimised to simultaneously maximise the cell count and growth, as well as the yield of the obtained FI and the resistance of the probiotic to simulated gastric conditions after 7 days of storage at 25 °C, minimising pH and nutrient loss (proteins and carbohydrates) in the washing water. The optimal design conditions found were 60 h of incubation and 13 mL of water/g oat bran. The growth kinetics of L. acidophilus was determined for the optimal system, showing no lag phase and the maximum specific growth rate (µ_max) of 1.1 ± 0.1 h^- 1. The system with an optimal hydration level (13 mL/g oat bran) and 36 h of fermentation was selected for being scaled-up in one order of magnitude. A reduction in cell growth, in the FI yield, and an increase in the value of the titratable acidity of the recovered supernatants were observed. During the fermentation, the acids produced were mainly lactic acid followed by acetic acid. It must be highlighted that the fermentation process proposed, reduced the initial oxalic acid content in oat bran. The production of FI based on oat bran containing L. acidophilus represented a sustainable process that also improved the nutritional aspects of the raw material. Oat bran could be by itself an adequate support for L. acidophilus storage stabilisation.